During the lifetime of a patient, it may be necessary to perform a total shoulder replacement procedure on the patient as a result of, for example, disease or trauma. In a total shoulder replacement procedure, a humeral component having a head portion is utilized to replace the natural head portion of the arm bone or humerus. The humeral component typically has an elongated intramedullary stem which is utilized to secure the humeral component to the patient's humerus. In such a total shoulder replacement procedure, the natural glenoid surface of the scapula is resurfaced or otherwise replaced with a glenoid component which provides a bearing surface for the head portion of the humeral component.
Glenoid components have heretofore been designed which include a number of plastic inserts coupled to metal backings. The metal backings are provided to secure the plastic inserts to the glenoid surface of the scapula. However, use of such two-piece glenoid components has a number of drawbacks associated therewith. For example, it is possible over the useful life of the glenoid component for the plastic inserts to separate from the metal backing thereby necessitating replacement of the glenoid component. In addition, over time wear of the plastic insert inherently occurs at the interface between plastic insert and the metal backing. It is possible for the plastic insert to wear to a degree which necessitates replacement of the glenoid component. It should be appreciated that in either case, such replacement of the glenoid component requires the patient to again be subjected to a surgical procedure and the subsequent recovery period associated therewith.
In response to the shortcomings associated with two-piece glenoid component designs, a number of one-piece glenoid components have heretofore been designed. In regard to such one-piece designs, a body portion, having a bearing surface defined therein for receiving the head of the humeral component, has a number of attachment pegs integrally formed therewith. The attachment pegs are advanced and thereafter secured into a corresponding number of holes which are drilled in the glenoid surface of the scapula by use of bone cement. An example of such a one-piece glenoid component that is designed to be secured to the scapula by use of bone cement is disclosed in U.S. Pat. No. 5,032,132 issued to Matsen, III et al.
As with the two-piece designs, certain one-piece glenoid components which have heretofore been designed have a number of drawbacks associated therewith. For example, some studies have speculated that it may be desirable to secure artificial components to natural bone structures without the use of bone cement. Glenoid components which have been designed to be secured to the scapula by the use of bone cement generally cannot be secured to the natural glenoid without use of the same.
Many glenoid component designs have been manufactured to address different types of scapular deficiencies. For example, some glenoid components have anchor pegs with flexible fins that are designed to act as barbs when inserted into the scapula. Other designs may utilize glenoid components with a buttress extending from the glenoid to fill larger defects in the natural glenoid. These may also include anchor and/or stabilizing pegs. In other embodiments a vault-filling glenoid may be used to fill a natural glenoid that has severe defects.
However, one problem with even existing modular designs, is that they do not provide the surgeon with the option of using different designs once surgery has started. Also, if a kit was to include all the different sizes and variations, the kit would be quite large and cumbersome to bring into surgery.
Another problem is that glenoid bone quality and surface deterioration varies significantly from patient-to-patient. Therefore, in current designs, having standard peg or buttress or vault locations may not work with specific patients' anatomy.
Another problem faced by surgeons during the procedure is that if the glenoid is partially eroded, ligament tensioning may be less than ideal. In some prior art designs, a stepped glenoid is provided to allow the surgeon to fill the eroded glenoid. However, these glenoids come in predetermined sizes and the size of the step (height and width) may not appropriately fill the glenoid erosion.